What is an explanation of benefits?

The EOB is the paper trail between your doctor, your insurer, and you, and the first thing to know is what it is not: it is not a bill. Medicare's version makes this explicit - the Medicare Summary Notice states it is not a bill, it is a record of the claims processed for you. A private insurer's EOB works the same way: after a visit or prescription, the insurer logs what the provider charged, the negotiated plan rate, what the plan paid, and what remains as your responsibility - the number a real bill from the provider should match when it arrives. That matching step is the EOB's whole superpower. Read three lines: the service billed, the amount the plan paid, and the patient responsibility column. If the provider's later bill asks for more than the EOB's patient-responsibility figure, that gap is the dispute - call the provider's billing office with the EOB in hand, because balance errors are common and the EOB is your proof. The EOB is also how you catch fraud early: a claim for a service you never received, from a provider you never saw, is the signature of medical identity theft, and reporting it to the insurer protects you. And it is the scoreboard for your year: deductibles and out-of-pocket totals tick forward on EOBs, so watching them tells you when care gets cheaper. Most insurers default to electronic EOBs now - log in rather than tossing the envelopes. Pymander is a free AI doctor, 24/7 by text, and can help you decode a confusing one.